1. Field of the Invention
The present invention relates generally to fluid flowmeter valves and, more particularly, pertains to a novel push-pull type flowmeter valve which has the capability of maintaining a precise fluid flow control setting irrespective of the on-off position of the valve.
Needle control type valves are well known in the art of precision fluid flowmeter instruments. In gas and liquid chromatography, control valves having a needle flow control are utilized to serve several functions. First, the needle control element is precision machined so as to enable an operator to precisely control the amount of fluid flowing through the valve. Secondly, the needle control element is also utilized to prevent any flow of fluid through the valve by setting the needle to its fully closed position.
2. Discussion of the Prior Art
A type of flowmeter valve which is common in the prior art is illustrated in CHEMETRON Corporation's advertising brochure for flowmeters, dated December 1978. This brochure discloses a typical dual function needle control valve, and illustrates the basic parts and operation thereof. The valve is shown partially in cross-section, demonstrating a function wherein the turning of a control knob forces a needle control element into the fluid passageway within the valve and produces a smaller orifice through which the fluid may flow. Through continued turning of the control knob, the needle then fulfills its second function in abutting against the tapered orifice wall of the valve sleeve to effectively prevent fluid flow through the valve.
The problems associated with a dual function needle control valve of this type are numerous. Specifically, the configuration utilized to allow needle control type shut-off greatly decreases the operating life of the internal mechanical valve components. The precision machined edges of the needle control element readily become worn and unusable over a relatively short operating life span due to the repeated abutment of the needle against the edges of the valve sleeve, thereby resulting in a needle control having a restricted fine-setting capability. The effective operational life of the abutting wall of the valve sleeve is also decreased by the constant abutting action against the tapered needle, thereby also resulting in a needle valve control arrangement having a further reduced operating life. This loss of function necessitates frequent replacement of the needle and, if the abutment wall is also damaged or worn then, additionally, the entire valve sleeve must also be serviced or replaced.
Another major problem associated with needle shutoff valves of this type is the lack of control the original operator has over subsequent flow settings. Specifically, fluid flow control arrangements are often used in hospitals wherein both skilled and unskilled workers perform their daily work duties which, of course, include tending to the patients. After initially setting a flowmeter for a particular patient, it often becomes necessary, either for treatment or otherwise, to later temporarily turn off the flowmeter. Frequently, this turning off and resetting is not carried out by the original operator of the flowmeter, but by other personnel. Because of its dual function, after the needle flow control has been turned to its fully closed setting, the patient must then rely upon the accuracy of the new operator's memory to restore the flowmeter to its original setting. Unfortunately, the memory of the later operator is not always adequate to provide proper service and care to the patient. This may result in a patient receiving an overdose or underdose of a required fluid, with resultant dangerous or even tragic consequences to the patient.
The arrangements in the prior art which have sought to overcome the aforementioned problems have relatively complicated configurations and commensurately increased machining costs, and as a consequence thereof have achieved only limited success.
The invention herein described is drawn to a relatively inexpensive yet completely effective solution to the aforementioned problems. Although Loe U.S. Patent 4,064,908 is considered to be relevant prior art, the present invention uses a novel, simple design to accomplish what Loe seeks to achieve through a highly complicated mechanism.
In greater particularity, Loe discloses a valve designed with the on-off function of the valve being independent of and not controlled by the needle flow control. This is accomplished in Loe by providing a valve cartridge which is threadedly received within a bore in the valve body. An operator, seeking to turn the valve off, must turn the knob which rotates the cartridge and results in longitudinal movement thereof into its innermost position to shut off the fluid flow. This knob can then be turned in the opposite direction to rotate the cartridge out of the bore to allow fluid flow therethrough. The actual shut off mechanism involved is the abutment of the valve cartridge and the end "O" ring against an inwardly tapered wall. This abutment operation occurs in much the same manner as found in the previously discussed prior art. A needle-type metering valve is threadedly engaged in the cartridge which is carried within the sleeve. The only function of the needle control element is to meter the fluid flow within the cartridge, independent of the on-off function of the valve. In addition to the abutment and the specially threaded cartridge received by the bore of the valve, Loe further states that this threaded assembly is absolutely required because of the mechanical advantage it provides. The patient also states that in order to withstand the flow pressures involved within the valve, an elaborate, balanced, seal arrangement would be required without this mechanical advantage. Loe further discloses that if a push-pull type construction were utilized, additional O ring seals would be required to achieve a required balanced seal. Loe, however, presents a complicated answer to the aforementioned problems. Specifically, Loe requires two threadedly received parts, the cartridge and the needle control element. Also, the cartridge still uses an abutting operation as clearly taught in the prior art. This abutment of O rings leads to a shorter operating life of the valve as well as a more complicated configuration.
The invention described herein attains the advantages of an independent needle flow control, and also provides a valve which is more efficient and more economical to maintain and manufacture than the Loe valve. Contrary to the disclosure in the Loe patent, the invention incorporates a needle flow control valve with a push-pull type shutoff valve. The present invention provides a push-pull type shutoff valve which is relatively easy to use without requiring any mechanical advantages as it taught by Loe. Specifically, the present invention discloses a simple yet remarkably effective flowmeter valve with a precision needle control independent of the shutoff mechanism of the valve which has a simple configuration of O rings to provide effective seals between a bore and a valve sleeve, as well as a unique arrangement of planar array radial bores.
This simple configuration completely circumvents any need for a mechanical advantage because of the inherent balance in the design of the valve. Further, the present invention does not require additional machining or a cartridge type of configuration. This provides an inexpensive valve with an extended operating life because there is no internal abutting of any relatively movable parts, thereby providing a valve which has negligible wear and therefore a much longer operating life.
Additionally, Brown U.S. Pat. No. 3,707,994 and Landwehr U.S. Pat. No. 3,870,080 although not considered highly relevant, are included to show the general state of the related art. Brown, U.S. Pat. No. 3,707,994 provides a spring loaded device which is used to regulate the flow of air to pneumatic tools. Although Brown discloses an apparatus which utilizes a sliding mechanism, the apparatus does not have a needle valve control, but rather uses a trigger to both shut off the flow as well as to meter it. Landwehr U.S. Pat. No. 3,870,080 discloses a valve which is capable of metering the flow and temperature of water in a faucet. A cartridge in the valve controls the water temperature by axial displacement and controls the flow therethrough by rotational movement. The invention herein described has the advantage over this art by not being dependent on any rotational orientation, thereby allowing operators of the present invention to be able to more easily operate the valve herein described.